Thin-walled thermoplastic polymeric containers have been adapted for use to contain a wide range of products manufactured by cold fill and hot fill methods. The advantageous features of thin walled polymeric containers are well known including low cost container manufacturing and presentation of product in aesthetically pleasing lightweight shapes. New designs of these containers locate handgrips into the surface of the container. The handgrips generally comprise opposed indentations in the sidewall of the container. These indentations provide an accommodating fit for the thumb and fingers. While the indentations enhance the handling characteristics of the bottle relative to pouring liquid product from the bottle, the handgrip indentations have presented some problems.
The handgrips can evert quite easily due to hydraulic shock or thermal shock. This problem is particularly common in the 1.75-liter container commonly used in the liquor industry. The hydraulic shock created by dropping a full container less than two feet, a common practice when packing the full containers into a carton for transport, can cause conventional handgrip indentations to evert.
Containers for hot-fill applications have encountered problems with handgrips everting from thermal shock and expansion during the hot-fill process. The everted handgrip indentations take a set in the outwardly projecting position to such a point that the handgrips of the container will not revert to the initially designed, inwardly projecting configuration, upon cooling.
Known prior art handgrips commonly have walls with converging straight sides. The convergence angles of the prior art joined walls are all generally very obtuse and shallow. These containers are unsatisfactory in that such shallow and flat handgrips commonly evert. To solve this problem the prior art offers a solution of reinforcing the handgrip by providing at least one laterally oriented grip rib. Users, however, often recognize such prior art ribs as aesthetically unpleasing and as sacrificing grip feel. See, for example, U.S. Pat. Nos. 4,804,097, 4,890,752, 5,226,550, and 6,223,920.
U.S. Pat. No. 5,598,941 teaches a different solution, for the prevention of everting handgrips, than the previously cited art. The '941 patent discloses a hot-fill container having inwardly inset and opposed flex panels. Each of the flex panels includes a grip structure defined by a pair of flat inwardly directed wall sections conjoined to form a trapezoidal grip panel. Three sides of the conjoined wall sections define an inwardly directed rib. During the fill of the hot product, the flex-panels tend to absorb the thermal expansion and the three-sided inwardly directed rib serves to strength the grip panel to prevent it from everting. The combination of flex panels and rib facilitates the structural integrity of the bottle. However, such a bottle is complicated to manufacture and quality control issues arise concerning the geometry of the flex panels, grip panel, and three-sided rib. Flowing material through the blow molding process is difficult when using such complicated geometry. Further, the use of flex panels is aesthetically undesirable.
Therefore, it is an object of this invention to simplify yet strengthen the handgrip structure of a thermoplastic polymeric container to prevent everting of the handgrip due to hydraulic or thermal shock.